2048-bit key...I'm leery

[Derek Atkins]

For the first key you were just plain lucky.  Most likely the first or
second number you tried happened to be a prime, so it found its p and
q fairly easily.  Thats all.

The 10 minutes is much closer to the average expected time..  But the
probability is linear between the two primes you choose, so you happened
to choose _just before_ a prime.  Lucky you!

-derek